System and method for converting wind into mechanical energy

ABSTRACT

A system for converting an airflow into mechanical energy includes a drawtube and an airflow turbine capable of converting an airflow through the drawtube into rotational mechanical energy. The drawtube includes a tubular member with first and second open ends and a substantially planar leading edge member positioned in front of the first open end. As an airflow passes over the drawtube, a reduced pressure region results adjacent to the leading edge. The reduced pressure region in combination with counter-rotating eddies, or vortices, formed by the leading edge cause air to be drawn out of the first open end of the tubular member establishing an internal airflow which drives the turbine or other energy conversion device.

FIELD OF THE INVENTION

The invention relates to a system and method for converting an airflowinto mechanical energy, and more particularly, the invention relates toa system and method for collecting wind energy and converting the windenergy into useful energy forms.

BACKGROUND OF THE INVENTION

Many wind energy collection systems have been proposed in the prior art.Classic windmills and wind turbines employ vanes or propeller surfacesto engage a wind stream and convert the energy in the wind stream intorotation of a horizontal windmill shaft. These classic windmills withexposed rotating blades pose many technical, safety, environmental,noise, and aesthetic problems. The technical problems may includemechanical stress, susceptibility to wind gusts and shadow shock, activepropeller blade pitch control and steering, and frequent dynamicinstabilities which may lead to material fatigue and catastrophicfailure. In addition, the exposed propeller blades may raise safetyconcerns and generate significant noise. Furthermore, horizontal axiswind turbines cannot take advantage of high energy, high velocity windsbecause the turbines can be overloaded causing damage or failure. Infact, it is typical to govern conventional horizontal windmills at windspeeds in excess of 30 mph to avoid these problems. Since wind energyincreases as the cube of velocity, this represents a significantdisadvantage in that high wind velocities which offer high levels ofenergy also require that the windmills be governed.

Vertical axis turbines are also well known. Although vertical axisturbines address many of the shortcomings of horizontal shaft windmills,they have their own inherent problems. The continual rotation of theblades into and away from the wind causes a cyclical mechanical stressthat soon induces material fatigue and failure. Also, vertical axis windturbines are often difficult to start and have been shown to be lower inoverall efficiency.

One alternative to the horizontal and vertical axis wind turbinesdescribed above is the airfoil wind energy collection system describedin U.S. Pat. Nos. 5,709,419 and 6,239,506. These wind energy collectionsystems include an airfoil or an array of airfoils with at least oneventuri slot penetrating the surface of the airfoil at about thegreatest cross-sectional width of the airfoil. As air moves over theairfoil from the leading edge to the trailing edge, a region of lowpressure or reduced pressure is created adjacent to the venturi slot.This low pressure region, caused by the Bernoulli principal, draws airfrom a supply duct within the airfoil, out of the venturi slot and intothe airflow around the airfoil. The air supply ducts within the airfoilare connected to a turbine causing the system to draw air through theturbine and out of the airfoil slots thus generating power.

In the wind energy collection systems described in U.S. Pat. Nos.5,709,419 and 6,239,506, the slot, or the area just aft of the leadingedge and prior to the tubular section, was a low pressure area used fordrawing air out of the airfoil. However, it has been found that the drawwas developed by only a small portion of the slot, that coinciding withthe very beginning of longitudinal opening on the tubular member.Therefore, the goal seemed to be a wider opening. However, as theopening was enlarged, the performance dropped off after the size of theopening reached a width equal to or greater than the width of theleading edge. Accordingly, this established a limit on the size of theopening.

Accordingly, it would be desirable to provide a wind energy collectionsystem with non-moving wind contacting parts, which provides improvedefficiency and a stronger, simpler construction.

SUMMARY OF THE INVENTION

The present invention relates to a wind energy collection systemconstructed from one or more airfoils with substantially stationary windcontacting surfaces, a substantially flat leading edge and a scoop forimproved efficiency.

In accordance with one aspect of the invention, a system for convertingan airflow into mechanical or electrical energy includes a tubularmember, the tubular member having a first opening and a second opening,the first and second openings formed in two planes substantiallyperpendicular to a longitudinal axis of the tubular member; asubstantially planar leading edge member positioned on windward side ofthe first opening; and an energy conversion device configured to convertan airflow through the tubular member into mechanical or electricalenergy.

In accordance with another aspect of the invention, a system forconverting an airflow into mechanical or electrical energy includes adrawtube and an energy conversion device configured to convert anairflow through the drawtube into mechanical or electrical energy. Thedrawtube includes a tubular member with a circular cross-section, thetubular member having a first opening and a second opening, the firstand second openings formed in two planes substantially perpendicular toa longitudinal axis of the tubular member; a substantially planarleading edge member positioned on a windward side of the first opening;and a scoop member positioned on an opposite side of the second openingfrom the leading edge member, wherein the substantially planar leadingedge member and the scoop member are in two planes which aresubstantially parallel to the longitudinal axis of the tubular member.

In accordance with a further aspect of the present invention, a systemfor converting wind into mechanical or electrical energy including adrawtube and an energy conversion device configured to convert theairflow through the drawtube into mechanical or electrical energy. Thedrawtube includes a tubular member having a longitudinal axis, aninside, an outside, a first open end and a second open end; and aleading edge positioned adjacent to the outside of the first open end ofthe tubular member configured to create a pressure differential withinthe tubular member when wind blows past the drawtube generating anairflow within the tubular member.

In accordance with another aspect of the present invention, a method forcollecting wind energy includes the steps of: providing a drawtubecomprising a tubular member having a pair of openings extendingperpendicular to a longitudinal axis of the tubular member and asubstantially planar leading edge member positioned in front of one ofthe openings; positioning the drawtube in the wind with thesubstantially planar leading edge member facing into the wind; passingwind around the substantially planar leading edge member, the airflowcreating eddies in and around the tubular member and the substantiallyplanar leading edge member; creating an airflow within the tubularmember; and converting the airflow to mechanical or electrical energy.

The present invention provides the advantages of improved efficiency andimproved structural strength in a system for converting an airflow intomechanical energy with substantially stationary wind contactingsurfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe preferred embodiments illustrated in the accompanying drawings, inwhich like elements bear the reference numerals, and wherein:

FIG. 1 is a perspective view of a system for converting an airflow intomechanical energy in the form of a simple drawtube.

FIG. 2 is a perspective view of an alternative embodiment of the systemfor converting an airflow into mechanical energy in the form of acompound bidirectional drawtube.

FIG. 3 is a perspective view of another configuration of a compoundbidirectional drawtube according to an alternative embodiment.

FIG. 4 is a perspective view of one configuration of a unidirectionalcompound drawtube according to another embodiment.

FIG. 5 is a perspective view of a panel of three compound bidirectionaldrawtubes according to the present invention.

FIG. 6 is a perspective view of an array of the system for converting anairflow into mechanical energy according to the invention.

FIG. 7 is a perspective view of an alternative embodiment of anomni-directional compound drawtube with a rotating leading edge andscoop.

FIGS. 8A and 8B are perspective views of an alternative embodiment of acompound drawtube with sliding plates.

FIG. 9 is a perspective view of a system with embedded simple drawtubesaccording to one embodiment of the present invention.

FIG. 10 is a perspective view of a system including an array of primarycompound drawtubes with embedded compound drawtubes according to analternative embodiment of the present invention.

FIG. 11 is a side view of a system including an array of primarycompound drawtubes with embedded compound drawtubes and a single energyconversion device.

FIG. 12 is a top view of one of the primary tubular members of FIG. 11with an embedded compound drawtube.

FIG. 13 is a top view of the system of FIG. 11.

DETAILED DESCRIPTION

This invention provides a system for converting an airflow intomechanical energy with non-moving wind contacting parts and whichprovides improved efficiency with a stronger, simpler construction.

FIG. 1 shows a drawtube 10 for converting an airflow into mechanicalenergy having a tubular member 20, a substantially planar leading edgemember 30, and an energy conversion device 70. The wind in FIG. 1 isassumed to be coming out of the page. The energy conversion device 70may be positioned within the tubular member 20 as shown in FIG. 1 orconnected to the drawtube 10 by an air plenum. The tubular member 20 hasa first opening 22 and a second opening 24 formed in two planessubstantially perpendicular to a longitudinal axis X of the tubularmember. The substantially planar leading edge member 30 is positioned infront of or on the windward side of the first opening 22. The leadingedge member 30 in the embodiment of FIG. 1 is in a plane which issubstantially parallel to the longitudinal axis of the tubular member20, however, the leading edge may also be canted aft as will bedescribed further below. The tubular member 20 has a circularcross-section; however, it can be appreciated that the tubular sectioncan be oval, rectangular, or otherwise shaped without departing from thepresent invention. The substantially planar leading edge member 30 (orleading edge) causes a deep low static pressure region to be formedadjacent to the first opening 22 of the tubular member 20. This lowpressure region causes air to be drawn through the tubular member 20 inthe direction of the arrow A.

In order to increase the opening size of the wind energy collectionsystems as described in U.S. Pat. Nos. 5,709,419 and 6,239,506 withoutalso incurring the width-related performance penalty, the opening 22 wasplaced at substantially 90 degrees to the leading edge 30. This led tothe minimal design of the simple drawtube 10 of FIG. 1 consisting of thetubular member 20 with a circular end opening 22 and a substantiallyplanar member 30 (or leading edge) installed next to one opening 22. Thebottom opening 24 of the tubular member 20 can be connected to an airplenum (not shown), wherein the air plenum connects the drawtube 10 toothers, and/or to a mechanical-to-electrical energy conversion device.

In operation, the system 10 of FIG. 1 functions based on the generallyknown principle that within a system, the total pressure in the air isequal to a constant. In addition, the total pressure is also equal tothe sum of the dynamic, static, and potential pressure components. Inthis case, the potential pressure component remains constant.Accordingly, if the dynamic component, or the air velocity varies, thestatic component, or the absolute or gauge pressure, must vary by anequal and opposite amount, i.e.,PTOTAL=PDYNAMIC+PSTATIC=Cwhere

-   -   PTOTAL is the total pressure,    -   PDYNAMIC is the dynamic pressure, and    -   PSTATIC is the static pressure.

In the case of the present invention, the substantially planar leadingedge member 30 (or leading edge) accelerates the airflow (i.e., wind) ata point adjacent to an edge of the substantially planar leading edgemember 30. Velocities in this region can be many times greater than theambient winds. Accordingly, since the total pressure must remainconstant, the very high velocities also mean very low static pressuresadjacent an edge of the leading edge 30.

One of the particular advantages of the design of the present inventionis that in using a closed system, the user can benefit from both thestatic and dynamic components of the airflow. An open-air turbine ofconventional design, for example, can only harvest the dynamic pressurecomponent as the static pressure differentials dissipate into the openair. This is further compounded by the fact that the local air velocityis slowed substantially, by no less than about one-third, before it everreaches an open-air or conventional wind turbine. The effect of slowingthe approaching wind reduces the amount of energy that a wind turbinecan capture to an absolute maximum described by the Betz limit.Generally, it is acknowledged that all flat-plate bodies in the windslow the oncoming air velocity to about two-thirds (⅔) of the originalvelocity. Although the present invention is also restricted by the Betzlimit, a drawtube does increase the energy density through the energyconversion device by collecting energy across its overall flat-platearea.

Using traditional designs for wind turbines, the only way to increasethe amount of energy presented to the turbine at a given wind speed, isto increase the area, or the diameter of the propeller. To reach afivefold increase in energy, for example, one would have to increase thepropeller diameter by 2.236 times, since the area of the propellerincreases with the radius squared. In the real world of mechanicalstress and strain, not to mention clearance issues, gyroscopic forces,teetering, and all the other issues of large, open air props, suchincreases can be impractical.

In addition to differential pressures, strong leading edge vorticesformed adjacent to the edges of the substantially planar leading edgemember 30 also play a part in increasing the ability of the system togenerate energy. The leading edge vortices are tubular in nature, androtate in opposite directions, i.e., backwards with the wind and inwardstoward the area behind the center of the substantially planar leadingedge member 30. This strong rotational flow also helps to trap, entrainand draw along the airflow from within the outlet opening 22 of thetubular member 20. When the system 10 is canted with the leading edgemember 30 at about 33 degrees aft, these vortex tubes stay substantiallyfixed in position, thus increasing the performance. In a preferredembodiment the tubular member 20, leading edge 30, are both canted atabout 33 degrees. However, each of these members can be cantedindividually to achieve some of the benefits. The substantially planarleading edge member 30, being slightly less in width than the diameterof the tubular member 20, places the high velocity vortex tubes inoptimal position with respect to the circular tubular member 20 outletopening 22.

An aspect ratio, or height to width ratio of the entire drawtube, ofabout 6 to 1 is desirable because it allows a high velocity flow over a“bluff body” airfoil, which in turn creates high velocity vortices offthe substantially planar leading edge member 30. In addition, when thetubular member 20 is tubular, or cylindrical, it affords the lowestfriction solution to moving air within an enclosed, or interior, volume.It also presents a “bluff body” cross-section to the wind, whichencourages strong vortex formation.

As shown in FIG. 1, the wind energy system 10 includes the tubularmember 20, the substantially planar leading edge member 30, and theenergy conversion device 70 for converting the airflow into rotationalmechanical energy. The second opening 24 of the tubular member 20 isconfigured to form an air plenum. For the purposes of this application,the air plenum can be of any length and/or configuration and is thoughtof simply as an enclosed air passageway connecting the low staticpressure regions of the system 10 to a higher static pressure region,which may be either the outside air or an increased static pressureregion formed by the action of one or more scoops (shown in FIG. 2). Theair plenum in the example of FIG. 1 begins with the low pressure regionadjacent to the substantially planar leading edge member 30 and extendsthrough the tubular member 20 of the drawtube 10 to the second opening24.

The energy conversion device 70 is placed in the air plenum and convertsthe mechanical energy of a rotating turbine to electrical energy orother energy. Although the energy conversion device 70 has been shownwithin the tubular member 20, it may also be placed at a remote locationas illustrated in U.S. Pat. Nos. 5,709,419 and 6,239,506 which areincorporated herein by reference in their entirety.

In operation, the substantially planar leading edge member 30 ispositioned on the windward side of the tubular member 20 or in front ofthe tubular member. When an airflow, for example, a gust of wind blowspast the substantially planar leading edge member 30, the area adjacentthe first opening 22 of the tubular member 20 is at a low pressurecompared with the air pressure outside of the second opening 24 of thetubular member 20. This pressure difference causes air from within thetubular member 20 to flow out of the tubular member 20 through the firstopening 22.

According to one example, the substantially planar leading edge member30 is a plate-shaped member having a height which is about equal to aheight of the tubular member 20, and a width which is about equal to orslightly less than the width of the opening 22. The substantially planarleading edge member 30 is as thin as is structurally possible. Forexample, the planar leading edge may have a thickness of between about1/2400 to about 1/16 of the height of the substantially planar leadingedge member 30.

In another embodiment as shown in FIG. 2, a compound drawtube 100includes the tubular member 20, the substantially planar leading edgemember 30, the energy conversion device 70, and a scoop member 40. Thewind in this embodiment is assumed to be coming out of the page.However, the drawtube 100 also operates with wind going into the page.

In order to maximize performance, or the flow of air within the tubularmember 20 and/or plenum, an opposing, high pressure region can becreated. It has been shown that an increased positive pressure gradientis created by a scoop member 40, shown in FIG. 2. The placement of thescoop 40, if used, is at opposite ends of the tubular member 20, withthe energy conversion device placed within the tubular member andbetween the low pressure region of the drawtube adjacent the leadingedge 30 and the high-pressured region adjacent the scoop 40.

The scoop member 40 (or scoop) causes an increase in static pressure byconverting the dynamic component of the wind energy (dynamic pressure)in close proximity to the second opening 24 of the tubular member 20 tostatic pressure. The increase in the local static pressure at the secondopening 24 and the low static pressure at the first opening 22 createshigh velocity airflow through the interior of the tubular member 20 andthrough the turbine of the energy conversion device 70.

The present invention operates through the acceleration and decelerationof the wind, or airflow, based on the Bernoulli theory. It creates twodissimilar regions, one of high velocity, low static pressure and one oflow velocity, high static pressure, and then connects the two in acontrolled environment. The vortices carry high velocity air backwardsand inwards to interact with the wide circular outlet opening 22 on thetubular member 20. The lowest velocity air is created at the center of ablunt surface, such as the interface between the scoop member 40 and thetubular member 20 inlet opening 24. This interface is located at thelateral centerline of the scoop member 40 to take advantage of thelowest velocity air.

The compound drawtube 100, as shown in FIG. 2, is a bidirectional systemwherein both the substantially planar leading edge member 30 and thescoop member 40 can function as either the leading edge or the scoopdepending on the direction of the approaching wind. As shown in FIG. 2,if the wind or airflow were coming from the direction of the observer,the scoop member 40 would assume the role of the leading edge.Meanwhile, the substantially planar leading edge member 30 would assumethe role of the scoop. Conversely, if the wind or airflow were comingfrom the opposite direction, the substantially planar leading edgemember 30 would become the leading edge, and the scoop member 40 wouldbe the scoop. In most bidirectional systems the substantially planarleading edge member 30 and scoop member 40 have a substantially similardesign.

The leading edge is generally defined as a substantially planar memberpositioned on the windward side or in front of the tubular member 20.The leading edge member 30 is positioned adjacent to the outside of thefirst open end 22 of the tubular member 20. Meanwhile, the scoop isgenerally defined as a substantially planar member positioned on theleeward side or in back of the tubular member 20. The scoop 40 ispositioned adjacent to the outside of the second open end 24 of thetubular member 20. The tubular member 20 is configured to create apressure differential within the tubular member when wind blows past thecompound drawtube 100 generating an airflow within the tubular member.As discussed above with respect to FIG. 1, the energy conversion devicemay alternately be located outside of the drawtube 100 and connected byair passages.

FIG. 3 illustrates an alternative embodiment of a compound bidirectionaldrawtube 200 having two tubular members 20 and one rectangular leadingedge member 30 which operates with one of the tubular members dependingon the direction of the wind. The leading edge 30 also acts as a scoopwith the other tubular member thus increasing the pressure differentialand, ultimately, the airflow within the tubular members 20 c and 20 d.In the embodiment of FIG. 3, when the wind is blowing in the directionof the arrows C, the planar leading edge 30 operates in combination withthe tubular member 20 c to create an airflow in the direction FC throughthe tubular member 20 c. The leading edge 30 also operates as a scoopfor the tubular member 20 d when the airflow is in the direction C. Whenthe airflow is in the direction of the arrows D, the leading edge 30operates as a leading edge in combination with the tubular member 20 dto create an airflow in the direction FD through the tubular member 20 dand operates as a scoop for tubular member 20 c. One difference betweenthe drawtube 100 of FIG. 2 and the drawtube 200 of FIG. 3, is that thecompound drawtube of FIG. 2 is better suited for an internal energyconversion device or embedded drawtube, whereas the compound drawtube ofFIG. 3 is better suited (but not limited to) for a plenum mounted energyconversion device, such as you might see in an array.

FIG. 4 illustrates an alternative compound drawtube configuration withtwo tubular members 20 e interconnected by a planar leading edge 30.When the wind blows from the wind direction E the planar leading edge 30operates as a leading edge for both of the tubular members 20 e and theairflow through the tubular members 20 e is as shown. If the wind is inthe opposite direction, the planar leading edge 30 becomes a scoop andthe airflow direction is reversed. As in the single direction drawtube10 of FIG. 1, the single direction drawtube 300 of FIG. 4 may be mountedon a rotation mechanism for allowing the drawtube to rotate so that theplanar leading edge 30 faces into the wind. The rotatable supportstructure for rotating the drawtubes may be any of those which are knownto those in the art.

The Tubular Member

As shown in FIGS. 1 and 2, the tubular member 20 has a circularcross-section. However, the tubular member 20 can be slightly oval, orcomposed of planar sections with connecting angles in an approximationof a circular cross-section (as shown in FIGS. 8A and 8B). Theperformance should increase as the drawtube approximates a cylinder. Inaddition, it can be appreciated that other shapes and configurations ofthe tubular members can be used.

As shown in FIGS. 1 and 2, the tubular member 20 has an interior surface26 and an exterior surface 28. In one embodiment, the interior surface26 of the tubular member 20 is smooth and as free as possible fromobstructions of any sort. If any obstructions are required, they arepreferably oriented longitudinally, not laterally, or cross-flow. Theexterior surface 28 of the tubular member 20 is also smooth. If exteriorobstructions are required, the obstructions are preferably lateralrather than longitudinal.

The Drawtubes

The size and shape of the drawtubes 10, 100, 200, 300 as shown in FIGS.1-4, are based on the availability of aerodynamic propellers,generators, local ordinances and covenants (including heightrestrictions), and ease of installation and maintenance. However, it canbe appreciated that the drawtubes 10, 100, 200, 300 can be constructedto almost any dimension. In other words, the aerodynamic performanceremains predictable as the size of the drawtubes 10, 100, 200, 300increase until the point where the wind speed off the substantiallyplanar leading edge member 30 approaches the speed of sound. Inaddition, as the size of the drawtubes 10, 100, 200, 300 decreases, theperformance characteristics remain the same as long as turbulent flow ispossible.

In one embodiment, the simple drawtube 10 of FIG. 1 has a height towidth ratio of about six-to-one (i.e., the total height of the drawtube10, including the tubular member 20 and the substantially planer leadingedge member 30). When three components, two tubular members and onesubstantially planar member (FIG. 3), or one tubular member and twosubstantially planar members (FIG. 2), are combined, the system forms acompound drawtube. In each case, simple or compound, the resultingaerodynamic system can have an aspect ratio of about 6:1. Additionally,each component should approximate the aspect ratio of each othercomponent in the system. For instance, in a simple drawtube, the twocomponents can each have an aspect ratio of about 3:1. In the compounddrawtube however, each component would have an aspect ratio of about2:1.

Although drawtube aspect ratios of about 6:1 have been described, it canbe appreciated that other ratios can be used. For example, height towidth ratios of about 2:1 to about 100:1 can be used. Preferably aheight to width ratio of about 4.5:1 to about 10:1 is used. The lengthof each section (i.e., the tubular member 20, the substantially planarleading edge member 30 and the scoop member 40) is about equal inlength.

The Leading Edge and Scoop

The substantially planar leading edge member 30 and the scoop member 40are generally rectangular shaped planar members. However, it can beappreciated that other shapes can be used including square, oval, orother shapes that provide a leading edge vortex. In addition, thesubstantially planar leading edge member 30 and the second planar member40 are as thin as possible, unobstructed, and straight. In oneembodiment, the substantially planar leading edge member 30 issubstantially flat. However, it can be appreciated that thesubstantially planar leading edge member 30 can have a curved or angledsurface for increased structural strength and for rotating the system toface the wind. The lateral width of the substantially planar leadingedge member 30 and the scoop member 40 can be slightly less than thediameter of the tubular member. In one embodiment, the lateral width ofthe substantially planar leading edge member 30 and the scoop member 40are about 13/16 of the diameter of the main body of the tubular member20.

The longitudinal length of the substantially planar leading edge member30 and the scoop member 40 should be tied to the aspect ratio (i.e.,longitudinal length to lateral width) of the overall drawtube 10, 100,200, 300. Each part of the drawtube 100, including the substantiallyplanar leading edge member 30, the scoop member 40, and the tubularmember 20, can be about one-third of the overall length of the drawtube100. Accordingly, if the drawtube 100 has a ratio of six-to-one, thelongitudinal length of each part of the drawtube 100 would be aboutone-third of the total length of the drawtube 100, or two times thediameter of the tubular member 20. The substantially planar leading edgemember 30 can be almost any size and can be formed in a variety ofdifferent shapes.

As shown in FIG. 5, the substantially planar leading edge member 30 andthe scoop member 40 have an interior surface 32, 42 and an exteriorsurface 34, 44, respectively. The exterior surfaces 34, 44 face awayfrom the tubular member 20. Meanwhile, the interior surfaces 32, 42 facetoward the tubular member 20.

In one embodiment, the exterior surface 34 of the substantially planarleading edge member 30 (leading edge) does not have longitudinalobstructions. However, if longitudinal obstructions are used such as forsupport members, they preferably are not placed near an edge of thesubstantially planar leading edge member 30. In addition, the interiorsurface 32 of the substantially planar leading edge member 30 preferablydoes not have longitudinal obstructions near the edges either. Theinterior surface 32 of the substantially planar leading edge member 30is flat; however, it can be curved or shaped otherwise.

The scoop member (scoop) 40 is either curved or flat. For bidirectionaldrawtubes 100, 200 as shown in FIGS. 2 and 3, without designrestrictions other than performance, both the scoop member 40 and thesubstantially planar leading edge member 30 are substantially flat,since both will alternate roles as the leading edge and scoop. Inaddition, the interior surface 42 of the scoop member 40, (i.e., theside facing the drawtube 100) is preferably free of obstructions. Ifobstructions are used, such as for support members, on the side facingthe drawtube 100, they can be arranged longitudinally if possible andkept away from the edges. As shown in FIG. 5, a smooth exterior surfacecan be achieved by placing longitudinal supports 52 on the interiorsurfaces 32, 42 of the substantially planar leading edge 30 and thescoop member 40.

The substantially planar leading edge member 30 is substantiallyrectangular in shape. In addition, the scoop member 40 is substantiallyrectangular for the bidirectional drawtubes of FIGS. 2 and 3, and hasthe same shape as the substantially planar leading edge member 30.However, it can be appreciated that other shapes can be used.

In one embodiment of the present invention, the substantially planarleading edge member 30 and the scoop member 40 are attached directly tothe first and second openings of the tubular member 20. Thesubstantially planar leading edge 30 and the scoop member 40 have alongitudinal and lateral width wherein the longitudinal length isgreater than the lateral width creating a long edge and a short edge.The tubular member 20 is connected to a middle portion of the short edgeof the substantially planar leading edge member 30 and the scoop member40. The windward side of the transition between the substantially planarleading edge member 30 and the scoop member 40 to the tubular member 20is smooth without air gaps. In addition, an outside lateral edge 54, 56of the substantially planar leading edge member 30 and the scoop member40, respectively, are not fared into the tubular member 20. Rather, theoutside lateral edges 54, 56 are free to contact the wind.

The drawtubes 10, 100, 200 are preferably placed on an inclination fromabout 0 degrees aft to about 60 degrees aft, and more preferably about33 degrees aft (away from the wind). In other words, the plane of theleading edge 30, the axis of the tubular member 20, and the plane of thescoop 40 are all angled at an angle of about 33 degrees to the verticalwith the free end of the leading edge positioned aft and the free end ofthe scoop forward.

In operation, the “performance to angle of inclination” curve climbssmoothly from about one, or the reference point for a drawtube 10, 100,200 with the drawtube parallel to, and facing into the wind, toperpendicular, to a peak at about 33 degrees aft (at twice theperformance of perpendicular), and then drops back down crossing thesame level as perpendicular at about 45 degrees aft and then continuesdownward back toward reference when the drawtube 10, 100, 300 is, onceagain, parallel to the wind.

Energy Conversion Devices

The energy conversion device 70 is used to convert the airflow (i.e.,wind) into mechanical energy (rotational, pneumatic, etc.) and/orelectrical energy. In one embodiment, the energy conversion device 70 isan airflow turbine positioned within the tubular member 20. However, itcan be appreciated that the energy conversion device 70 can be any typeof conversion device known to one skilled in the art that can be used toconvert the airflow into mechanical energy. For example, the energyconversion device 70 can be a rotational mechanical to electrical energyconverter, a device which utilizes the pneumatic pressure differentialsbetween the high and low static pressure regions, such as a jet pump orventuri nozzle, or a device which transfers the mechanical energy of arotating propeller to a mechanical device outside the drawtube.

The energy conversion device may be located remotely and connected tothe drawtube 10, 100, 200, 300 by a system of air passageways or airplenums. The remotely located energy conversion device may be a turbine,jet pump, or the like connected to one or more drawtubes by airpassages. The energy conversion device may convert wind to mechanicalenergy, electrical energy, or a combination thereof. The mechanicalenergy created may include rotation of a propeller or turbine blade, ahigh velocity airflow, or other mechanical energy. The mechanical energymay be used directly or used to generate electrical energy.

In an alternative embodiment, the system uses an aerodynamic propellerto collect and convert the airflow into rotational mechanical energy.The mechanical energy is then converted through an electrical generatorinto electrical energy.

The energy conversion device 70 or aerodynamic propeller/generator isplaced at the center of the tubular member 20, or within the air plenumand between the drawtube induced low-pressure region and the scoopmember 40. However, it can be appreciated that other locations can bechosen without departing from the present invention.

For a bidirectional drawtube 100, 200 as shown in FIGS. 2 and 3, theenergy conversion device 70 will produce power with airflow in eitherdirection. For example, an aerodynamic propeller with a low camber, anda generator capable of producing power in either rotational directioncan be chosen. In another embodiment, a permanent magnetgenerator/alternator passing through a bridge rectifier can be employed.

As shown in FIG. 2, the air plenum containing the energy conversiondevice 70 is generally confined to the tubular member 20 of the drawtube100. For FIG. 3, the energy conversion device 70 is generally locatedoutside of the drawtube 200 in an air passageway connected to thedrawtube. Generally, the drawtubes 100 will have a wider angle ofefficacy when placed vertically. Although the invention has beenillustrated with the drawtubes 100 positioned vertically, the drawtubescan be positioned horizontally or at any other angle.

Arrays of Drawtubes

An array can be any plurality of the drawtubes 10, 100, 200, 300described above or any combination thereof. The arrays described hereinare merely some of the possible array arrangements.

FIG. 6 shows a plurality of drawtubes 100 for collecting energy such asthose shown in FIG. 2 configured in a fixed, fence-like, or lateralarray 210. The fence-like array 200 is preferably constructedperpendicular to the predominant winds.

Although the possible variations of arrays are endless, the increasedperformance of the drawtubes 10, 100, 200, 300 by a variation of arraysis unique to this design. As shown in FIG. 6, the fence-like array 400is constructed in a fence-like fashion, composed of connecting sections,or panels 210. Each panel 210 of three drawtubes 100, four of which areshown in FIG. 6, support a plurality of drawtubes 100. In FIG. 6, thepanels 210 shown are angled at about 30 degrees with respect to theadjacent panels. In this embodiment, the “fence-like” array 400 zigzagsacross the ground for increased stability. In operation, each panel 210of three drawtubes 100 produces about 500 watts, yielding a total ofabout 2 kW for an array of four panels 210. In addition, each array 200is designed to be modular, such that a customer can simply add as manypanels 210 as required to meet the desired level of output power.

The panels 210 have a space between drawtubes 100 of about one to threetimes the diameter of the drawtubes 100. This increases the output ofeach drawtube. The optimal spacing between drawtubes is about 1.25diameters. This fence array is just an example of the many possibletypes of arrays. The array 200 creates an air passageway thataccelerates the airflow between the drawtubes 100, thus increasing theperformance and output of each individual drawtube 100, and hence thearray 200.

Generally, the substantially planar leading edge member 30 and scoopmember 40 are placed perpendicular to the wind. In other words, the flatsurfaces of the substantially planar leading edge member 30 and scoopmember 40 face into the wind. However, when winds are as much as 45degrees to either side of perpendicular, an array 200 of drawtubes 100can function at close to full power. Typically, an array 200 ofdrawtubes 100, can produce rated power for incoming winds that fallwithin two triangular regions, 90 degrees wide, on each side of thearray 200. In most favorable sites, there are prevailing wind patternsin opposed directions, for example onshore and offshore breezes.

Although an array of the drawtubes 100 of FIG. 2 have been illustratedin FIG. 6 many other array configurations may be used. The leading edge30 and/or scoop member 40 may not be in a one-to-one ratio with thenumber of tubular members 20. For example, in an alternative embodiment,a system can use a single substantially planar leading edge member 30 toserve a plurality of tubular members 20.

In FIG. 3, the substantially planar leading edge member 30 and the scoopmember are combined into one surface. In other words, the substantiallyplanar leading edge member 30 and the scoop member 40 are simultaneouslyboth the leading edge for one tubular member 20 c and the scoop for theother tubular member 20 d. Thus, when the wind direction changes, theroles of the combined substantially planar leading edge member 30 andthe scoop member 40 change. An array of the drawtubes 10 of FIG. 1 maybe assembled end-to-end, or longitudinally, in this same fashion usingone leading edge and/or scoop between every two tubular members.

In addition, the linear arrangement as shown in FIG. 4, or the staggeredarrangement as shown in FIG. 3, wherein the leading edge and/or scoopshares a surface with its two neighboring tubular members, alsodecreases the cost of materials. Each of these choices, as examplemodels of array connectivity, offers its own advantages and may bebetter suited to different conditions in the field. In addition, it canbe appreciated that an array of drawtubes can be constructed with twosets of features, those inherent to a lateral array, and those inherentto a longitudinal array, by combining both designs into one array.

However, it can be appreciated that the array need not be linear orstaggered. For example, the outline of the array can be curved or in acircular fashion. In addition, as long as the distance between tubularmembers 20 is equal to or more than about seven times their diameter,the tubular members 20 can be placed downwind of other tubular members20 in the same array, as in a circular lateral array. For example, athree-dimensional version of a circular array can be a spherical orhemispherical array. This would involve tubular members 20 in arrays inboth the lateral and longitudinal directions, and would look like theframe of a geodesic dome.

The tubular members 20 are generally placed vertically in arrays.However, it can be appreciated that in an alternative embodiment, atleast two tubular members 20 can be arranged horizontally and assembledtogether in an end-to-end fashion in an array. Then at least two tubularmembers 20 share a substantially planar leading edge member and/or scoopmember.

In an alternative embodiment, a plurality of smaller drawtubes 10, 100,200, 300 can be implemented instead of a single drawtube 10, 100, 200,300 if the overall height of a wind system is a concern. The pluralityof drawtubes 100 can be arranged either in a vertical or horizontalarrangement, wherein the total or sum of the electrical or mechanicalenergy product of the smaller drawtubes 100 in the array can equal thetotal power of a single drawtube 100 having substantially largerdimensions, without incurring the dimensional penalties of the single,larger drawtube 100.

In addition, it is often found that a plurality of smaller drawtubes 100is also easier to manipulate than a single, larger drawtube 100. It canalso be appreciated that the drawtubes 100 can be designed so that eachdrawtube 100 can be easily lowered for maintenance or inspection.Generally, there is no limit to the size or number of drawtubes 100included in an array and the number of drawtubes 100 will depend on theoverall objectives and the availability of materials. For example, aplurality of very small drawtubes 100, formed from extruded aluminum,can be a practical solution in a mesh-like or a chain link fence array.

Movable Systems

As described above, in one embodiment the substantially planar leadingedge member 30 and scoop member 40 are perpendicular to the prevailingwind or airflow. However, if the wind directions are not consistent, analternative embodiment as shown in FIG. 7 can be implemented. As shownin FIG. 7, a single compound drawtube 110 is constructed in a fixedposition. In this embodiment, the substantially planar leading edgemember 30 and the scoop member 40 rotate independent of the tubularmember 20 to face into the wind. The substantially planar leading edgemember 30 and the scoop member 40 are rotated utilizing either amotorized linkage, or through aerodynamic means by placing the centersof aerodynamic pressure for the scoop and the leading edge aft of thepivot points. In this embodiment, the scoop member 40 and thesubstantially planar leading edge member 30 do not serve as both a scoopand a leading edge, such that the substantially planar leading edgemember 30 and the scoop member 40 can be optimized for its own function.The scoop member 40 and the substantially planar leading edge member 30can be inclined aft at an angle, between about 0 degrees to about 60degrees and generally about 33 degrees aft, with respect to thelongitudinal axis of the tubular member.

The system 110, as shown in FIG. 7, is omnidirectional and it operatesequally well under winds from any direction. Furthermore, the tubularmember 20 can be structurally fixed in one position for increasedstrength. In an alternative arrangement, the leading edge and scoop canbe fixed while the tubular member can be canted and rotatable to providea drawtube which is convertible to two opposite directions.

In an alternative embodiment, such as the embodiments of FIGS. 1 and 4,the entire drawtube 10, 300 including the tubular member(s) 20, thesubstantially planar leading edge member 30, and the optional scoopmember 40 are rotatable. The drawtube 10, 300 rotates utilizing a set ofbearings centered on the longitudinal axis. The drawtube 10, 300 can bemotorized to face into the wind, or, alternatively, the center of theaerodynamic pressure could be placed aft of the pivot points.

In another embodiment, as shown in FIGS. 8A and 8B, the system can betransformed, through sliding or rotating panels. FIG. 8A shows astylized system 410 composed of a plurality of sliding panels 130, 140mounted on the sides of a rectangular, tubular member 120 or themultiple-sided approximation of a cylinder. As the wind directionchanges, the sliding panels 130, 140 slide up or down, as shown in FIG.8B to form the substantially planar leading edge member 130 and thescoop member 140. This system is also omni-directional. These alternateembodiments are not meant to be all inclusive, but are intended to showthat many other manifestations of the basic design are possible andpractical without changing the process as described in this application.

Embedded Drawtubes

FIG. 9 shows an alternative embodiment of a system 500 for collectingenergy from wind in the form of an embedded drawtube in which one ormore embedded inner drawtubes are positioned within the tubular members,or plenum, of an outer drawtube, or system. An embedded drawtube mayinclude either a simple or compound drawtube or an array of simple orcompound drawtubes that are actually placed inside the tubular member ofa larger drawtube or system. The embedded drawtubes are installed inplace of the energy conversion device in the tubular members of thelarger system. This additional level of energy collection andconcentration can be used where the primary, or larger stage, drawtubesor array of drawtubes can be constructed inexpensively. The embeddeddrawtube system yields doubly reduced static air pressures which, whencompared to the outside static pressure, or especially an increasedoutside static pressure through the use of a scoop, will drive a smallerenergy conversion device within the secondary embedded drawtube systemat a much higher energy level.

The embedded drawtube system 500 of FIG. 9 includes a compound drawtube510 having two tubular members 520 a, 520 b and a leading edge/scoop530. The primary drawtube 510 is constructed in this example as abidirectional drawtube in which one of the tubular members 520 aoperates with the leading edge 530 with the wind direction out of thepage as shown by the arrows G. When the wind is out of the page, theother tubular member 520 b operates with the scoop 530 to generateairflow through the tubular member 520 b in the direction shown. Whenthe wind is reversed, the airflow through the tubular members 520 a, 520b is also reversed. The embedded drawtubes 540 illustrated in FIG. 9 arethe simple drawtubes of FIG. 1 and are placed across the airflow, oracross the axis of the tubular members 520 a, 520 b. The inner drawtubes540 may also be any of the compound drawtubes or drawtube arraysdiscussed above. The inner drawtubes 540 each include a planar leadingedge/scoop 544 and a tubular member 542. The tubular member 542 isconnected by an air passageway 550 to an energy conversion device 560.

The inner drawtubes 540 in the embedded drawtube system 500 have a smallair plenum diameter and high pressure differential which allows the useof certain energy conversion devices 560 such as jet pumps which may notbe possible at larger diameters and smaller pressure differentials. Theuse of a jet pump as an energy conversion device 560 is particularlybeneficial as they have no moving parts and can be made to convert abidirectional airflow to a unidirectional product airflow. The energy ofa jet pump may be used directly to power a remote air conditioner, waterpump, or other pneumatic device. In the embodiment of FIG. 9, theembedded drawtubes 540 are canted at an angle X with respect to a lineperpendicular to the axis of the primary tubular member 520.Alternatively, the embedded drawtubes 540 can have a planar leading edge544 which may be canted at the angle X. As described above, the angle ofcanting may be about 0 to about 45 degrees and is preferably about 33degrees.

The primary drawtube 510 produces a high energy airflow through theinteraction of both high and low pressure regions when the drawtube isplaced within an airflow. The embedded secondary drawtubes 540 produce avolume of air with a static pressure reduced even further than thestatic pressure available within the air plenum of the primary drawtube.The smaller, secondary drawtube 540, once placed within the primary airplenum, receives an enhanced airflow possessing up to about five timesthe energy density of the outside air stream. Since the system efficacyincreases with the apparent wind speed, the embedded or secondarydrawtube 540 creates an additional deep static pressure reduction. Whenthis is compared to the outside ambient air, a twofold reduction isrealized. This, in turn, creates increased airflow within the secondaryair plenum.

An energy conversion device as shown and described herein, can beinserted within the tubular member 542 of the embedded drawtube 540 orremote from the system as shown in FIG. 9.

The primary drawtube 510 and embedded drawtube 540 preferably have anaspect ratio of about 6:1 as described above. In one embodiment, thelength to diameter restriction, coupled with the preferred leading edgeaft inclination of about 33 degrees, leads to an embedded secondarydrawtube 540 having a diameter of 5/24 of, or 0.2083 times the diameterof the primary drawtube 510. The internal area of the embedded secondarydrawtube 540 would, in this embodiment, be about 1/23 of the internalarea of the primary drawtube 510.

It can be appreciated that the design tradeoff for embedding drawtubesdepends on the cost of construction, the characterization of availablepropellers and generators, and the time weighted average of the expectedwind regime.

If, for instance, an array of primary drawtubes can be constructedinexpensively, embedded secondary drawtubes can be effectively inserted.The added benefits are that smaller diameter collection plenums andenergy conversion devices can also be used. Also, the embedded secondarydrawtubes 540 are in a more controlled environment, with winds alwaysapproaching at a preferred or correct angle. Although primary andsecondary drawtubes are shown, a system may include tertiary oradditional embedded drawtubes inserted inside the secondary drawtubes.

FIG. 10 shows a modular unit or system 600 for collecting energy fromthe wind having embedded drawtubes. As shown in FIG. 10, each verticalrow contains two larger, or primary, compound drawtubes 610. Thedrawtubes 610 each include a tubular member 620, a leading edge 630, anda scoop 640. The drawtubes 610 are arranged such they share a common thescoop member 640. Within each of the primary tubular members 620 is anembedded compound drawtube 650 of the type illustrated in FIG. 3.However, other embedded drawtube embodiments, or arrays of embeddeddrawtubes may be used. The two vertical rows of the modular units arestaggered vertically, so that a preferred 33-degree inclination isachieved when embedded drawtubes 650 are connected via the secondary airplenums 660 to the energy conversion devices 670.

Of course, the energy conversion device 670 could assume many forms,within or outside the embedded drawtubes 650. Since the two primarycompound drawtubes 610 in a vertical row face in opposite directions,the airflow within each primary drawtube 610 is also in oppositedirections as shown by the arrows H. This causes the flow in eachembedded drawtube 650 to flow in opposite directions as well with theflow through the secondary air plenums 660 in the direction of thearrows I.

As shown in FIG. 10, it is assumed that the wind is moving toward themodule from the direction of the observer. Therefore, the substantiallyplanar leading edge member 630 is positioned forward and the scoopmember 640 is positioned aft. If the wind reversed directions, theinternal flows would reverse and the substantially planar leading edgemember 630 and the scoop member 640 would reverse roles as well as theleading edges of the embedded drawtubes 650.

Also, an array of this type can be assembled using one or more of thesemodules, with additional modules added either vertically orhorizontally, or both. The module can be constructed so that twofunctional modules could be simply plugged together. As previouslymentioned, other types of arrays, embedded or not, such as thosepresented in this application, are both practical and possible.

The drawtube arrays illustrated are merely a few examples of the typesof arrays which are possible. The drawtube arrays may be connected suchthat a plurality of drawtubes are connected to a single air passagewayfor connection to one or more remote energy conversion devices. Forexample, a plurality of drawtubes of FIGS. 1, 2, 3 or 4 arrangedhorizontally, one above the other, may be interconnected by a pair ofvertically oriented air plenums formed at the ends of the arrays.

FIG. 11 illustrates a system 700 of compound drawtubes 710 where each ofthe compound drawtubes is arranged with two or more tubular members 720a, 720 b and three or more leading edge/scoop members 730, 740, 750. Thetubular members 720 a, 720 b and planar members 730, 740, 750 arearranged in a staggered arrangement as illustrated in the top view ofFIG. 13. As shown in FIG. 12, each of the tubular members 720 a, 720 bcontains one or more compound drawtubes 724 positioned at an anglewithin the tubular member as described in further detail in theembodiment of FIG. 10. The ends of these embedded compound drawtubes 724are connected to air passageways 760 (see FIG. 11) which run verticallyalong the sides of the tubular members 720 a, 720 b. The air passageways760 connect the embedded drawtubes 724 to an energy conversion device770 which may be positioned below the array 700, either on the ground orunderground. In the configuration of FIG. 11, the air passageways on oneside of the array will have an airflow in one direction, while the airpassageways on an opposite side of the array will have an airflow in anopposite direction.

While the invention has been described in detail with reference to thepreferred embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made and equivalentsemployed, without departing from the present invention.

1-35. (canceled)
 36. A system for converting an airflow into mechanicalor electrical energy comprising: a tubular member, the tubular memberhaving a first opening and a second opening, the first and secondopenings formed in two planes substantially perpendicular to alongitudinal axis of the tubular member; a leading edge memberpositioned on a windward side of the first opening; and an energyconversion device configured to convert an airflow through the tubularmember into mechanical or electrical energy.
 37. The system of claim 36,wherein the leading edge member is in a plane which is substantiallyparallel to the longitudinal axis of the tubular member.
 38. The systemof claim 36, wherein the tubular member has a circular cross-section.39. The system of claim 36, wherein the leading edge member has a widthwhich is about equal to or less than a diameter of the tubular member.40. The system of claim 36, wherein the energy conversion device is aturbine.
 41. The system of claim 36, wherein the leading edge has acurved surface.
 42. The system of claim 36, wherein the leading edge hasan angled surface.
 43. A system for converting an airflow intomechanical or electrical energy comprising: a drawtube, the drawtubecomprising: a tubular member with a circular cross-section, the tubularmember having a first opening and a second opening, the first and secondopenings formed in two planes substantially perpendicular to alongitudinal axis of the tubular member; and a leading edge memberpositioned on a windward side of the first opening; and a scoop memberpositioned on an opposite side of the second opening from the leadingedge member, wherein the leading edge member and the scoop member are intwo planes which are substantially parallel to the longitudinal axis ofthe tubular member; and an energy conversion device configured toconvert an airflow through the tubular member into mechanical orelectrical energy.
 44. The system of claim 43, wherein the leading edgemember has a width which is about equal to or less than a diameter ofthe tubular member.
 45. The system of claim 43, wherein the scoop memberhas a width which is about equal to or less than a diameter of thetubular member.
 46. The system of claim 43, further comprising a meansfor positioning the drawtube into the airflow, wherein the leading edgemember is facing substantially into the airflow.
 47. The system of claim43, wherein the drawtube is canted away from the airflow at an angle ofabout 0 to about 45 degrees with a free end of the leading edge memberpositioned aft and a free end of the scoop positioned forward
 48. Thesystem comprising a plurality of the drawtubes of claim 43, wherein theplurality of drawtubes are assembled in an array of two or moredrawtubes.
 49. The system of claim 43, wherein a plurality of theleading edge members are positioned at an angle of between about 25 to40 degrees to one another.
 50. The system of claim 43, furthercomprising a support structure for rotatably supporting the drawtube,the support structure orienting the drawtube so that the substantiallyplanar leading edge member is facing into the airflow.
 51. The system ofclaim 43, further comprising a support structure for rotatablysupporting the leading edge member and the scoop so that the leadingedge member is facing into the airflow.
 52. The system of claim 43,wherein the energy conversion device is positioned within the tubularmember.
 53. The system of claim 43, wherein the energy conversion deviceis positioned outside the tubular member and is connected to the tubularmember by an air passageway.
 54. The system of claim 43, wherein theleading edge has a curved surface.
 55. The system of claim 43, whereinthe leading edge has an angled surface.
 56. The system of claim 43,wherein the scoop member has a curved surface.
 57. A system forconverting wind into mechanical or electrical energy, the systemcomprising: a drawtube comprising: a tubular member having alongitudinal axis, an inside, an outside, a first open end and a secondopen end; and a leading edge positioned adjacent to the outside of thefirst open end of the tubular member configured to create a pressuredifferential within the tubular member when wind blows past the drawtubegenerating an airflow within the tubular member, the leading edge havinga curved surface; and an energy conversion device configured to convertthe airflow through the tubular member into mechanical or electricalenergy.
 58. The system of claim 57, further comprising a supportstructure for rotatably supporting the drawtube, the support structureorienting the drawtube so that the leading edge is faced into the wind.59. The system of claim 57, further comprising an airflow directionsensor and a motor for rotating the drawtube in response to the airflowdirection sensor.
 60. The system of claim 57, wherein the leading edgemember is in a plane which is substantially parallel to the longitudinalaxis of the tubular member.
 61. The system of claim 57, furthercomprising an embedded drawtube with an inner tubular member and aninner leading edge within the tubular member and located with alongitudinal axis of the embedded drawtube positioned across an axis ofthe tubular member.
 62. A method for collecting wind energy comprising:providing a drawtube comprising a tubular member having a pair ofopenings extending perpendicular to a longitudinal axis of the tubularmember and a leading edge member positioned in front of one of theopenings; positioning the drawtube in the wind with the leading edgemember facing into the wind; passing wind around the leading edgemember, the airflow creating eddies in and around the tubular member andthe leading edge member; creating an airflow within the tubular member;and converting the airflow to mechanical or electrical energy.
 63. Themethod of claim 62, further comprising positioning a scoop member inback of a second opening of the pair of openings.
 64. The method ofclaim 62, further comprising assembling a plurality of drawtubes in anarray of at least two drawtubes.
 65. The method of claim 62, furthercomprising canting the drawtube away from the wind at an angle of about0 to about 45 degrees with a free end of the leading edge memberpositioned aft of a forward edge of the tubular member.
 66. The methodof claim 62, further comprising positioning the drawtube on a supportstructure for rotatably supporting the drawtube, the support structureorienting the drawtube so that the substantially planar leading edgemember is facing into the wind.